Effect of wastewater colloids on membrane removal of microconstituent antibiotic resistance genes

Anthropogenically generated antibiotic resistance genes (ARGs) are considered emerging contaminants, as they are associated with a critical human health challenge, are persist independent of a bacterial host, are subject to transfer between bacteria, and are present at amplified levels in human-impacted environments. Given the gravity of the problem, there is growing interest in advancing water treatment processes capable of limiting ARG dissemination. This study examined the potential for membrane treatment of microconstituent ARGs, and the effect of wastewater colloids on their removal. Native and spiked extracellular vanA (vancomycin resistance) and blaTEM (β-lactam resistance) ARGs were tracked by quantitative polymerase chain reaction through a cascade of membrane filtration steps. To gain insight into potential associations occurring between ARGs and colloidal material, the wastewater colloids were characterized by scanning electron microscopy, as well as in their protein, polysaccharide, and total organic carbon content. The results suggest that extracellular DNA (eDNA) containing ARGs interacts with wastewater colloids, and can both be protected against degradation and be removed more efficiently in the presence of wastewater colloidal material. Thus, ARG removal may be achievable in sustainable water reuse scenarios using lower cost membranes than would have been selected based on molecular size alone. As membranes are likely to play a vital role in water sustainability, the results of this study enable consideration of ARG removal as part of a comprehensive strategy to manage emerging contaminants and to minimize overall public health risks.